During a computer system startup, the computer system is self-tested and initialized through loading and execution of system firmware. Under personal computer (PC) architectures, this firmware is commonly referred to as the system's Basic Input/Output System (BIOS). In a typical PC architecture, the BIOS is the firmware that runs between the processor reset and the first instruction of the Operating System (OS) loader. The BIOS provides a basic set of instructions used to boot the computer. The BIOS performs the tasks that need to be done at startup including performing self diagnostics and initializing the hardware in the computer, such as the Power On Self Test (POST) which determines if the computer keyboard, random access memory, disk drives, and other hardware are working correctly. The BIOS also acts as an interface between software and hardware components of a computer system during the OS runtime. For example, the BIOS manages data flow between the operating system running in the computer and the attached devices such as the hard disk, video adapter, keyboard, mouse, and printer. As computer systems have become more sophisticated, the operational environment between the application and OS levels and the hardware level is generally referred to as the firmware or the firmware environment.
The firmware is typically stored in non-volatile memory, such as Read-Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), and Electrically Erasable, Programmable, Read-Only Memory (EEPROM) or flash memory. Non-volatile memory retains the stored data after the power is removed for a period of time. The firmware may also be partially stored in volatile memory, powered by a battery to retain the stored data when the system is powered off. For example, Complimentary Metal Oxide Semiconductor (CMOS) Random Access Memory (RAM) is a small amount of volatile memory in a special RAM chip that stores the real time clock settings and configuration information for a PC. Plug-and-Play BIOS uses additional non-volatile memory to hold Extended System Configuration Data (ESCD). This is used to store system resource settings of system devices such as IRQs and I/O addresses. The content in the CMOS RAM is maintained with power from a small battery when the system is powered down. The BIOS typically provides a setup program which allows the user to adjust a variety of settings related to the BIOS operation and hardware setup such as CPU Clock speed, memory timing, time and date functions, disk configuration, etc.
Frequently, a large number of servers are used to meet the demand for computing power. A server rack typically host a number of server chassis stacked one over another vertically. To further increase the server density, multiple blade servers are designed to co-exist in one server chassis. Typically, a blade server is essentially a server computer on a circuit board, which can be installed into a slot in a server chassis. Multiple blade servers in one server chassis typically share one power supply. Thus, a blade server rack can have a number of server chassis stacked one over another vertically, with each chassis hosting a number vertically oriented blade servers arranged side by side in a row.